Add Pyodide WebAssembly wheel support

[zardus]

Build pypcode as a Pyodide-compatible WebAssembly wheel while preserving native and macOS cross-build paths.

The target build produces the nanobind extension with Emscripten, while a separate host CMake build produces the SLEIGH compiler needed to generate processor specifications. The existing build workflow now builds and exercises the Pyodide wheel.

Tandem PRs:

• Support wasm32 hosts in VEX basic types vex#82
• Add wasm32 Pyodide wheel support pyvex#555
• Select the Pyodide Z3 build on Emscripten claripy#737
• Make native-only loaders optional on Emscripten cle#702
• Add first-class WebAssembly runtime support angr#6658

Validation:

• 46 tests and 187 subtests pass natively
• all pre-commit hooks pass
• the Pyodide wheel imports and translates x86-64 instructions
• the full angr fauxware browser smoke test passes with the P-code engine

[zardus]

Tandem PRs — please test these together:

• Support wasm32 hosts in VEX basic types vex#82
• Add wasm32 Pyodide wheel support pyvex#555
• Select the Pyodide Z3 build on Emscripten claripy#737
• Make native-only loaders optional on Emscripten cle#702
• Guard optional UEFI dispatch registration cle#703
• Test CLE under Pyodide cle#704
• Add Pyodide WebAssembly wheel support #283
• Add first-class WebAssembly runtime support angr#6658

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.82%. Comparing base (559aacd) to head (3e6f4ad).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #283   +/-   ##
=======================================
  Coverage   86.82%   86.82%           
=======================================
  Files           5        5           
  Lines         516      516           
  Branches       82       82           
=======================================
  Hits          448      448           
  Misses         26       26           
  Partials       42       42           

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